Why Can’t Oil and Gas Analysis Prevent Transformer Explosions?

Most transformers are equipped with an On-Line Dissolved Gas Analyzer to measure the concentration of gases such as hydrogen, acetylene, ethylene, methane, carbon monoxide, etc. This equipment is used as a preventive action for slow moving changes in the dielectric properties of the oil due to humidity, moisture and particles from the winding insulation degradation. On-Line DGA’s are ideal for checking the long-term evolution of transformer corposant from oil to paper, etc.

However, transformer short-circuits occur without warning every day, producing catastrophic explosions and fires. Most of these incidents occur on transformers that are equipped or monitored by DGA’s, proving that oil and gas analysis can’t prevent an explosion. The response time of the sensors used for analyzing the oil and gas can vary from 10 to 40 minutes. Since a transformer explodes within milliseconds of a short circuit, it is simply not possible to receive the On-Line DGA results and decide whether to trip the transformer before an explosion occurs.

Furthermore, when most transformer explosions occur, the oil and gas analysis results are normal, even perfect. An example of this is the transformer explosion which happened at the James FitzPatrick Nuclear Power Plant. It was reported* that:

“All test results and monitoring data prior to the transformer failure indicated it was operating appropriately. There was nothing observed that would indicate the transformer would fail.”

Basically, a short circuit can occur at any time and the best way to prevent the transformer tank from explosion is to equip it with a TRANSFORMER PROTECTOR (TP). During the first milliseconds of the short circuit, the first Mega Joule creates a volume of 2.3m3 of explosives gases inside the transformer tank. At the same time, a dynamic pressure peak travels inside the tank at the speed of sound inside the oil, 4,000 ft/sec (1200 m/sec). The dynamic pressure peak activates the TRANSFORMER PROTECTOR (TP) within milliseconds and creates an opening for the oil and gas to be evacuated before static pressure increases.